Page 8, Item Box 1d. Proceeds, Paragraph 1:
Box 1d. Proceeds. "Enter the gross cash proceeds from all dispositions (including short sales) of securities, commodities, options, securities futures contracts, or forward contracts. Show a loss, such as one from a closing transaction on a written option or forward contract, as a negative amount by enclosing it in parentheses."
Seems clear to me that negative amounts in the proceeds box are allowed.
Changing the proceeds to zero and entering the loss as a positive amount in the basis box will result that the total proceeds amount in your Schedule D will be different from the total proceeds amount reported to the IRS, on the 1099-Bs. I expect this will be one of the checks by the IRS to see whether you reported your stuff correctly. It might be wise to attach an explanation then for the difference.
